The invention relates to a method for inspecting an integrated circuit, the circuit comprising a plurality of sub-circuits and the method comprising a determination of a first supply current in a supply line of a first sub-circuit of the sub-circuits.
The invention further relates to an integrated circuit comprising a plurality of sub-circuits and comprising a current-measuring device for measuring a supply current in a supply line of at least one of the sub-circuits.
Such method and circuit are known from the Japanese Patent Application published under JP-A 62-278473. The known circuit comprises a number of sub-circuits and a current-detection circuit. Each sub-circuit has in its supply line a controllable switch which can connect the sub-circuit to the current-detection circuit in order to supply power to the sub-circuit. At a certain moment, one or more of the sub-circuits are connected to the current-detection circuit and the current-detection circuit measures the current to those connected sub-circuits. The not-connected sub-circuits do not receive power and are therefore not operational. The known circuit has a drawback in that the controllable switch in the supply line of the sub-circuit influences the behaviour of the sub-circuit even when such switch is closed. Depending on the implementation, the switch causes a voltage drop in the supply line and adversely affects the dynamic behaviour of the sub-circuit. In practice it is desirable to measure the current flowing into one sub-circuit at a time, because this will give the most accurate measurement of the current. The known circuit then has a disadvantage in that only the sub-circuit connected to the current-detection unit is operational and that the other sub-circuits remain in-operational. In the case that the sub-circuits are tightly coupled, as for example in a complex analogue integrated circuit, an in-operational sub-circuit may have an unpredictable influence on the current consumption in another, operational sub-circuit and may even damage a sub-circuit.